1. Field
An ion exchanger, a method of manufacturing the same, and an ion exchange filter device and an electro-deionization device including the same are disclosed herein.
2. Description of the Related Art
A separation technology for selectively permeating cations and anions using an ion exchange membrane includes an electro-dialysis (ED) process and an electro-deionization (EDI) process. According to the ion concentration of water, the electro-dialysis process is used when the ion concentration is high, and the electro-deionization process is used when the ion concentration is low. The electro-deionization process for treating low ion concentration uses an ion exchange resin that may promote ion transfer, in order to reduce electrical resistance that may be generated and decrease protons and hydroxide ions generated by concentration polarization.
The ion exchange resin is not easy to handle due to its bead shape, and the removal efficiency may be decreased due to a decrease in flow rate, effective reaction area, and the like, which may be caused by partial tilting of the ion exchange resin during operation because of gravity. Further, since the effect on the throughput efficiency may be varied according to the charge density of the ion exchange resin, it is important to install it with a constant density, which is difficult if not impossible.
To overcome drawbacks of the ion exchange resin, various ion conductive spacers are being developed. As the example of the ion conductive spacer, an ion exchange fiber is suggested. The ion exchange fiber may be prepared by producing radicals on a polymer substrate using various irradiation sources such as UV, plasma, and the like on a polyolefin-based polymer substrate such as polypropylene, polyethylene, a polypropylene-polyethylene copolymer, and the like, and forming a branched copolymer while a new polymerization reaction occurs when the polymerizable monomers are contacted starting from the radicals. The ion exchange fiber has merits of being light-weight, and having convenient filter preparation and a fast ion exchange speed. If the ion exchange fiber is applied for an electro-deionization device, a high permeability coefficient may be obtained, and a reaction efficiency decrease over time may be overcome. However, the ion exchange fiber has limits as to how large the volume of the fiber can be and has a low charge density (low ion exchange capacity).
To compensate for drawbacks of the ion exchange fiber, a composite filter has been suggested wherein ion exchange resin particles having high ion exchange capacity are combined with the ion exchange fiber using a solvent-type adhesive. For example, a backbone substrate formed of reticular polyurethane foam is impregnated with an adhesive such as one that is acryl-based, urethane-based, vinyl acetate-based, and the like, and an ion exchange resin is attached to the backbone substrate to prepare an ion exchange filter device. However, when the adhesive covers the ion exchange resin particles, ion exchange capacity may be decreased, and the manufacturing process is complicated due to the use of the adhesive.
Although there is an attempt to introduce an ion exchange functional group in the backbone substrate such as reticular polyurethane foam and the like, there is a problem of low ion exchange capacity.